Check for *_exporter before import ansible deployed cluster

[AstroProfundis]

Feature Request

Is your feature request related to a problem? Please describe:

For an ansible deployed tidb cluster, if the node_exporter or blackbox_exporter is not deployed properly, the imported cluster may fail to upgrade in later operations.

An example of user report about this case is available on AskTUG.

Describe the feature you'd like:

We need to find a way to either:

• Check for broken node_exporter or blackbox_exporter before importing the cluster, or
• Automatically deploy the agents after imported the cluster

Describe alternatives you've considered:

We have the automatically upgrade process for prometheus and alertmanager for imported cluster, maybe we can do this in a similar way?

Teachability, Documentation, Adoption, Migration Strategy: